1. Field of Invention
The present invention relates generally to semiconductor devices and more particularly to radio frequency (RF) switches for use in RF applications.
2. Related Art
FIG. 1 illustrates an exemplary transceiver 100 of the prior art coupled to an antenna 110. The transceiver 100 includes a switch 120, such as a solid-state single pole double throw switch, configured to switch between a power amplifier 130 and a receiver amplifier 140. The transceiver 100 further includes filters 150 disposed between the switch 120 and the antenna 110.
In the prior art, the antenna 110 is sometimes coupled to multiple circuits each comprising a switch 120, power amplifier 130, and receiver amplifier 140, where each such circuit is dedicated to a particular frequency band. Here, the transceiver 100 handles one or more high bands and/or one or more low bands, for example. In these instances the filters 150 selectively remove frequencies outside of the particular frequency band to which the circuit is dedicated.
Most of the power being produced by the power amplifier 130 is at some desired frequency, however, some power also goes into harmonics of that primary frequency. Accordingly, another function of the filters 150 is to remove the higher harmonics of the transmitted signal so that the antenna 110 only transmits at the desired frequency.
In operation, the transceiver 100 transmits an RF signal by coupling the power amplifier 130 to the antenna 110 and receives an RF signal by coupling the receiver amplifier 140 to the antenna 110. It will be appreciated, however, that since the power amplifier 130 and the receiver amplifier 140 are both coupled to the same switch 120, the switch 120 can unintentionally couple the high-power transmitted RF signal onto the receiver transmission line 160, an effect known as parasitic leakage.
Additionally, the switch 120 needs to be able to handle the high voltages produced by the power amplifier, in the range of about 15 to 30 volts. Such voltages are too high for metal oxide semiconductor (MOS) switches to withstand.